Shit happens is a common vulgar slang phrase, used as a simple existential observation that life is full of unpredictable events, either "Así es la vida" or "C'est la vie". The phrase is an acknowledgment that bad things happen to people seemingly for no particular reason.[1][2] The phrase was first observed in 1964, but wasn't used in a print publication until 1983. Alternately said, albeit less vulgarly, as "stuff happens".[3]

The fact that people have been remarking that shit happens has been attested from 1964, when Carl Werthman quoted an example in his UCBMA thesis; the relevant excerpt was published in The American City (edited by Anselm L. Strauss) in 1968.[4]

In the 1994 movie Forrest Gump, Forrest runs into dog droppings and a man in the bumper sticker business brings it up. Forrest says "It happens," to which the man asks "What, shit?" and Forrest answers "Sometimes."

^The datum: "That shit happens all the time." In "The Police as Perceived by Negro Boys", ed. Carl Werthman; in The American City: A Source Book of Urban Imagery, edited by Anselm L. Strauss (Chicago: Aldine, 1968), p. 285. Here in Google Books. A footnote says that Werthman's short contribution to the book is "Excerpted from 'Gang members and the police', unpublished M.A. thesis, University of California, Berkeley, 1964."